WordPress 定时关闭评论以及告知用户评论关闭的时间

/**
 * WordPress 告知用户评论关闭的时间
 * http://www.wpdaxue.com/automatic-comment-closing.html
 */
add_action( 'comment_form_top', 'wpdx_comment_closes_in' );
function wpdx_comment_closes_in() {
    global $post;
    if ($post->comment_status == 'open') {
        $close_comments_days_old = get_option( 'close_comments_days_old' );
        $expires = strtotime( "{$post->post_date_gmt} GMT" ) +  $close_comments_days_old * DAY_IN_SECONDS;
        printf( __( '(该文章的评论功能将在 %s 后关闭)', 'domain' ),  human_time_diff( $expires ));
    }
}